The LCD (Liquid Crystal Display) possesses many advantages of being ultra thin, power saved and radiation free. It has been widely utilized in, such as LCD TVs, mobile phones, Personal Digital Assistant (PDA), digital cameras, laptop screens or notebook screens, and dominates the flat panel display field.
Most of the liquid crystal displays on the present market are backlight type liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The working principle of the liquid crystal display panel is that the Liquid Crystal is injected between the Thin Film Transistor Array Substrate (TFT array substrate) and the Color Filter (CF). The light of backlight module is refracted to generate images by applying driving voltages to the two substrates for controlling the rotations of the liquid crystal molecules.
The TFT array substrate comprises a plurality of gate lines and a plurality of data lines. The plurality of gate lines and the plurality of data lines, which are orthogonal with each other, form a plurality of pixel units, and each pixel unit comprises a Thin Film Transistor (TFT), a pixel electrode and a storage capacitor. The TFT comprises a gate coupled to the gate line, a source coupled to the data line, and a drain coupled to the pixel electrode. When the gate lines is driven, the TFT is in an on state, the gray scale voltage signal is sent to the corresponding data line and loaded to the pixel electrode thereby. Thus, the corresponding electrical field generates between the pixel electrode and the common electrode. The liquid crystal molecules in the liquid crystal layer has orientation change under the function of the electrical field, and thus to realize the image display.
In the liquid crystal display device according to prior art, with the influence of the capacitance coupling effect, as the TFT is activated and deactivated, the stability of the data signal voltage will be influenced, and then, the image quality is affected. Therefore, it is required to chamfer the TFT activation voltage VGH to reduce the voltage difference between the TFT activation voltage VGH and the TFT deactivation voltage VGL as the TFT is deactivated to diminish the influence to the data signal voltage. Specifically, referring to FIG. 1, the method of grounding and discharging the resistor is commonly used in prior art to achieve the objective of chamfer. As shown in FIG. 1, the chamfering circuit according to prior art comprises: an Integrated Circuit (IC) 10 and a chamfering circuit 20; one end of the chamfering circuit 20 is coupled to the Integrated Circuit 10, and the other end is grounded; referring to FIG. 2, the TFT activation voltage VGH generated by the Integrated Circuit 10 is discharged and chamfered with the chamfering resistor 20. For the chamfering resistor 20 of the same resistance, the chamfered waveform formed by the TFT activation voltage VGH is the same. Because the chamfered waveform will influence the pixel charge time to result in the H-block (Horizontal Block) phenomenon. Thus, it is required to control the chamfered waveform of the TFT activation voltage VGH to reduce the influence to the pixel charge time and to prevent the H-block phenomenon. Accordingly, it needs to replace the chamfering resistor 20 to find out the best resistance which has the smallest influence to the pixel charge time. The operation of such method is complicated and the work efficiency is low.